extra room? Bedroom? office? family space? I suppose it would depend on what I want to do in that room. I am a big believer in one accent wall in every room. What color are the other walls? White? Go with a deep green or Teal, or be very brave and go with maroon or terra cotta. It also depends on the furniture you have for the room. Neutral colors means you can go wild with your imagination. After you find the right accent color for the wall to match your ideas, then you find a really BIG painting or mirror or poster with complimenting colors and frames. Go big, go bright, be daring.